776 research outputs found
Optical IP switching a solution to dynamic lightpath establishment in disaggregated network architectures
The landscape of the telecommunications environment is constantly evolving; in terms of architecture and increasing data-rate. Ensuring that routing decisions are taken at the lowest possible layer offers the possibility of greatest data throughput. We propose using wavelengths in a DWDM scheme as dedicated channels that bypass the routing lookup in a router. The future trend of telecommunications industry is, however, toward larger numbers of interlinked competing operator networks. This in turn means there is a lack of a unified control plane to allow current networks to dynamically provision optical paths. This paper will report on the concept of optical IP switching. This concept seeks to address optical control plane issues in disaggregated networks while providing a means to dynamically provision optical paths to cater for large data flows
Serving Unaffiliated Distance Learners: Strategies that work
Dealing with unaffiliated distance learning students can be a daunting task for many public as well as academic librarians. This article will discuss strategies for providing reference to these students by gathering information on what services they are offered via their home institutions, and helping them navigate the often confusing landscape of library resources and services. Authors will outline the challenges and opportunities for public libraries presented by distance learners and suggest some services that might be provided for them. Finally, we will discuss the opportunities for outreach to distance learning students from both public and academic libraries
An Anomalous Phase in the Relaxor Ferroelectric Pb(ZnNb)O
X-ray diffraction studies on a Pb(ZnNb)O (PZN) single
crystal sample show the presence of two different structures. An outer-layer
exists in the outer most 10 to 50~m of the crystal, and undergoes a
structural phase transition at the Curie temperature K. The
inside phase is however, very different. The lattice inside the crystal
maintains a cubic unit cell, while ferroelectric polarization develops below
. The lattice parameter of the cubic unit cell remains virtually a
constant, i.e., much less variations compared to that of a typical relaxor
ferroelectric, in a wide temperature range of 15 K to 750 K. On the other hand,
broadening of Bragg peaks and change of Bragg profile line-shapes in both
longitudinal and transverse directions at clearly indicate a structural
phase transition occurring.Comment: to be submitted for PR
Operational reliability assessment of the GEOS A spacecraft
Decision theory application to GEOS A spacecraft operational reliability assessmen
Diffuse Neutron Scattering Study of a Disordered Complex Perovskite Pb(Zn1/3Nb2/3)O3 Crystal
Diffuse scattering around the (110) reciprocal lattice point has been
investigated by elastic neutron scattering in the paraelectric and the relaxor
phases of the disordered complex perovskite crystal-Pb(Zn1/3Nb2/3)O3(PZN). The
appearance of a diffuse intensity peak indicates the formation of polar
nanoregions at temperature T*, approximately 40K above Tc=413K. The analysis of
this diffuse scattering indicates that these regions are in the shape of
ellipsoids, more extended in the direction than in the direction.
The quantitative analysis provides an estimate of the correlation length, \xi,
or size of the regions and shows that \xi ~1.2\xi , consistent with
the primary or dominant displacement of Pb leading to the low temperature
rhombohedral phase. Both the appearance of the polar regions at T*and the
structural transition at Tc are marked by kinks in the \xi curve but not
in the \xi one, also indicating that the primary changes take place in a
direction at both temperatures.Comment: REVTeX file. 4 pages, 3 figures embedded, New version after referee
cond-mat/010605
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